Metabolic Flexibility Following High-Intensity Interval Exercise in Active Females: Effect of Feeding State

Metabolic flexibility is tightly regulated during exercise through the action of metabolites and metabolic enzymes. This randomized parallel-group study aimed to investigate how fed vs fasted state high-intensity interval exercise (HIIE) changes Glucose, lactate, pyruvate dehydrogenase kinase-4 (PDK-4), and carnitine palmitoyltransferase-1 (CPT-1) levels. 23 active females (20.09 ± 1.04 years of age) were selected from eligible volunteers and were randomly assigned into fed and 14-h fast groups. In each group, 6 participants randomly performed 1:4 HIIE (1 min all-out run, 4 min walk, for 20 minutes), and the other participants were seated. After a 5-minute cooldown, blood samples were collected from the brachial vein. Higher lactate levels were similar after HIIE in both feeding states. Fed-HIIE participants showed lower glucose levels, and fast-HIIE participants showed lower PDK-4 and CPT-1 levels than their control counterparts. It seems in the fasted 1:4 HIIE, glucose oxidation is the dominant energy production pathway. Lactate produced during exercise may be used as the precursor of gluconeogenesis in fasting.